"8253 PIT - Recently rewritten after microcontroller-based research. At least one previously undocumented feature discovered. Accurate enough for PCM audio."
... and it turns out that it's this ...
https://github.com/dbalsom/martypc/blob/main/core/src/device...
// If the counting element was reloaded between load of LSB and MSB, it is an incomplete load.
// Reload the counting element again when we get the MSB.
// Note: This is completely undocumented behaviorAnd those debugging tools are something else, too!
https://youtu.be/yVO2VDPnI0Y (the first 1.5 minutes are fine to watch, the rest is of dubious worth)
Are there any cycle-accurate like this for 8-bit consoles?
That machine required very precise timing of the CPU to drive the video output.
There are a number of other cycle-accurate emulators, including some you woudln't expect, like a cycle-accurate emulator for the C64 floppy disk (needed for anti-piracy and some high-end demos that use the floppy like a co-processor).
[0] - https://emulation.gametechwiki.com/index.php/Nintendo_Entert...